In a known control device of this type, such as that described in French Pat. No. 2,249,425, the cam which is part of a timing mechanism is intended to actuate, once at each of its revolutions, a reversing switch which comprises three elastic conductive blades which are arranged side by side and are embedded at one end and which interact with the cam by means of their other respective ends supporting the actual contacts. Such a device has some disadvantages, particularly because of the presence of the elastic blades. In fact, since the respective ends of these blades support contacts interacting directly with the single notch of the control cam and since these blades work with a bending action, this results in a certain degree of inaccuracy as regards the actual moment of closing and opening of the switch, since, depending on whether the blades are more or less flexible because of their manufacture, they are capable of being actuated by the control cam at different moments. Moreover, since the profile of the cam is snail-shaped, the contacts, when in the closed position, constantly rub against one another during each revolution of the cam, thus causing permanent wear of the contacts and creating radio-electric disturbances. For the same reason, the contact pressure varies constantly during each revolution of the cam, the pressure being maximum when the blades rub against the highest part of the cam profile. Moreover, the blades actuate the contacts only once in each revolution of the control cam, and a complete revolution of the latter is necessary to bring the blades into the upper position ready to drop into the single notch again. This is a disadvantage when the said cam should be integral, for example, with a cam block designed to advance step by step and having a large number of steps per revolution, for example 60 steps. In fact, since the blades are flat up against the cam, it would be impossible to change the number of notches in such a proportion. Finally, to work correctly with a bending action, blades must have a relatively substantial length, and consequently the three blades described in the abovementioned patent have a relatively large bulk, and this prevents the possibility of certain uses of the control device of the prior art.